Turbine blade and vane platforms, from which blade and vane airfoil portions extend, can experience platform distress due to lack of adequate cooling. Hot gaspath air impinges on the downstream mateface wall, which augments the heat transfer and then penetrates the entire depth of the mateface. When this occurs, turbine blade and vane platforms experience localized heavy distress, such as thermo-mechanical fatigue (TMF), and oxidation. Turbine blades can experience the additional distress mode of creep. Such distress often occurs in regions where the airfoil trailing edge is in close proximity to the mateface. These regions are particularly difficult to cool because the platform edges are a considerable distance from the blade and vane core. This presents a manufacturing challenge in drilling long cooling holes into a region where limited space is available. There is therefore a need to reduce the penetration of gaspath air into the mateface regions, utilizing minimal cooling flow, in order to reduce turbine blade and vane platform distress.